CVE-2026-49477

Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser

State: Published
Severity: 7.5 High
Published: Jul 14, 2026
Updated: Jul 21, 2026
Reserved: May 30, 2026

Description

Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminated quoted value in soupsieve/css_parser.py, allowing an attacker who can supply untrusted CSS selector strings to soupsieve.compile() or Beautiful Soup .select() / .select_one() to cause CPU exhaustion and denial of service. This issue is fixed in version 2.8.4.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M

Weaknesses

CWE-400 Uncontrolled Resource Consumption
CWE-1333 Inefficient Regular Expression Complexity

Affected Products

Product	Versions
soupsievefacelessuser	< 2.8.4Affected

References

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